1. Technical Field
The present disclosure relates to the field of semiconductor technology and more particularly, to a method of manufacturing a semiconductor device.
2. Description of the Related Art
In the field of semiconductor technology, a static random-access memory (SRAM) device is a type of semiconductor device that is widely used in computers, mobile phones, digital cameras, and other electronic devices. In some SRAM devices, a fin-type field effect transistor (FinFET) may be used to increase the memory density and performance of a SRAM cell.
It is known that reducing the size of the SRAM cell can improve device performance. Although the width of the FinFET can be adjusted by changing its quantum number, the change may alter the characteristics of the semiconductor device. When the quantum number is changed, it may be difficult to use values obtained from the layout design of a SRAM device including the FinFET, since the design values could be different from the actual values of the manufactured device.
Generally, there are two methods to adjust the α, β, and γ ratios of a SRAM device to improve device performance, as described below.
In one method, different number of fin structures may be selected for the pull-up (PU) transistor, transfer gate (PG) transistor, and pull-down (PD) transistor. The number of fin structures may be provided in any combination, for example, (1, 1, 1), (1, 1, 2), or (1, 2, 3). For example, in the (1, 2, 3) combination, there is one fin for the pull-up (PU) transistor, two fins for the transfer gate (PG) transistor, and three fins for the pull-down (PD) transistor.
In another method, fin structures having different heights may be selected for the pull-up (PU) transistor, transfer gate (PG) transistor, and pull-down (PD) transistor of the SRAM device.
However, the above methods for adjusting the α, β, and γ ratios of a SRAM device have several deficiencies. For example, using different number of fin structures for the different transistors could alter (increase) the size of the SRAM cell. Also, using fin structures of different heights increases the complexity of the manufacturing process since it is often difficult to control the varying heights during fabrication.
Accordingly, there is a need for an improved method of manufacturing a semiconductor device. In particular, there is a need for a method that can be used to fabricate a SRAM device which meets performance specifications.